Since herbicides are chemicals important for saving weed control working and achieving high crop yield, research and development of new herbicides have been extensively conducted for a long time and numerous types of chemicals have been practically used. However, the need still continues for new chemicals having more effective weed control activity, particularly, new chemicals which can selectively control the growth of objective weeds in small application rates without causing injury to agronomic crops.
In croplands of corn, etc., triazine herbicides such as atrazine and acid anilide herbicides such as alachlor and metolachlor have been used. However, atrazine is not sufficient for controlling Graminaceous weeds, although effective for controlling broad-leaved weeds. Alachlor and metolachlor in turn exhibit a low controlling activity against active broad-leaved weeds, although effective for controlling Graminaceous weeds. No herbicide is found at present, which can control the growth of gramineous weeds and broad-leaved weeds simultaneously by sole application. Moreover, the above herbicides must be used in larger amounts and not environmentally suitable.
Under the above circumstances, the inventors developed and proposed novel triketone derivatives having thiochroman ring (WO97/03064), which is represented by the following compound. ##STR2##
WO97/08164 discloses structurally specific triketone derivatives having thiochroman ring, which are represented by the following compounds. ##STR3##
However, the proposed compounds are still insufficient in herbicidal activity particularly in foliage treatment of Graminaceous weeds.